NEWS OF THE WEEK MATERIALS
SCIENCE
DIAMOND-LIKE HYDROCARBONS Nanoscale molecules with diamond structure isolated from petroleum
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IAMONDOIDS — HYDROCAR-
bon molecules in which the carbon frame work has the structure of a diamond lattice—can be isolated in great vari ety from natural gas con densates, according to a team of organic chemists at ChevronTexaco Energy Re search & Technology Co. Rigid and durable, and with a variety of structures, these nanometer-sized molecules may be a promising new class of molecular building blocks, the researchers suggest. The simplest diamondoid, the tricyclic molecule adamantane, was isolated from petroleum in the 1930s and synthesized half a century ago. Di- and triamantanes have also been made in the lab, but most of the larger and more structurally complex mem bers of this class have not been available either synthetically or from natural sources. Now, Jeremy E. Dahl, Shenggao Liu, and Robert M. K. Carlson have isolated and crystallized more than 20 higher order polymantanes [Science, pub lished online Nov 29, http://wwwsciencemag. org/cgi/content/abstract/ 1078239}. These molecules con tain from four to 11 of the 10-car bon adamantane units that make up the diamond crystal lattice. The new molecules "are quite rigid and have well-defined struc tures," Carlson says. "Some are rodlike, and we've isolated a whole series of these of increas ing lengths. Some are helical, with different pitches, lengths, and diameters. Some are chiral, and HTTP://PUBS.ACS.ORG/CEN
we can separate the enantiomers." Liu adds: "We think they have real potential as molecular build ing blocks. "We've shown that they can be connected to one ; another and have various functionalities attached." "These are fundamen tally new materials that have probably never existed before except dissolved in petrole um," Dahl points out. "We think their properties will be very interesting." Other researchers think so, too. The new work "may reawak en interest in this important class of compounds," writes chemistry professor Alan E Marchand of the University of North Texas in a perspective that accompanies the publication. Functionalized small er diamondoid molecules have im portant pharmaceutical applica-
tions, Marchand points out, par ticularly 1-aminoadamantane, an antiviral drug that is also used to treat Parkinson's disease. "Increasing the tool chest of molecules with interesting prop erties is part of the game of nanotechnology" says Wade Adams, director of the Center for Nano scale Science & Technology at Rice University. "I don't know whether this class of materials is ever going to amount to anything superspectacular, but they are very cool molecules." Like diamonds, the new / molecules have great thermal stability, and the Chevron/ Texaco chemists took advan tage of this property to isolate / them. After first identifying a petroleum distillate fraction enriched in the molecules, the researchers heated the fraction to 450 °C to destroy less stable hydrocarbons. T h e diamondoids can be separat ed from one another by shape-selective chromatog raphy and further purified by crystallization. Current proce dures produce the materials "in quantities that would be useful for high-end applications," Carlson says.-REBECCARAWLS
COURTESY 01 JEREMY Ε DAHL
SPARKLERS Hydrocarbon molecules, 1 to 2 nm in size, with characteristic diamond structure, are shown both inside and outside a diamond crystal lattice.
CONSOLIDATION
Chemical Operations On The Move •our chemical companies are shutting down units and relocating operations. In three of the cases, jobs are being cut. BP Solvay Polyethylene says it will close 260 million lb per year of high-density poly ethylene capacity at its Deer Park, Texas, fa cility in the first half of 2003. The company will replace the capacity with a 700 million-lb plant it is building in partnership with Chevron Phillips Chemical in Cedar Bayou, Texas. It hasn't determined how many jobs will be lost. Eastman Chemical is moving a coatings tech nology center from Carpentersville, III., to its Kingsport, Tenn., headquarters. The company says there will be 50 to 60 fewer jobs in Carpen tersville, although 40 jobs will move to Kingsport. Manufacturing will continue at the Car pentersville site, which came with Eastman's
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2000 purchase of McWhorter Technologies. Sovereign Specialty Chemicals is closing a waterborne adhesives plant in Cincinnati that employs 118 people. The company is moving production to Greenville, S.C., and Carol Stream and Plainfield, III., over the next nine months. Sovereign is also stopping waterborne and hot-melt adhesives production in Kapellen, Belgium. And the 1.25 billion-lb-per-year methanol unit in Fortier, La., that Methanex idled in March 1999 is probably down for good; the company is taking an after-tax charge of $86 million in the fourth quarter to write it off. Last month, Methanex announced it is build ing a 1.8 billion-lb methanol plant in Punta Arenas, Chile, where it already has more than 6 billion lb of methanol capacity—ALEX TULL0
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